1. Field of the Invention
Embodiments of the invention generally relate to apparatus and methods for processing semiconductor substrates. More particularly, embodiments of the present invention relate to apparatus and methods for processing a substrate near an edge region.
2. Description of the Related Art
To reduce the cost of ownership, semiconductor manufacture processes may be performed in an integrated system that is capable of processing multiple substrates in parallel with high repeatability. The integrated system usually comprises a factory interface, a loadlock chamber and a substrate deposition chamber adapted to form a deposition film on one or more substrates by chemical vapor deposition (CVD) or plasma enhanced chemical vapor deposition (PECVD) processes.
During the CVD/PECVD process, it is usually desirable to have a uniform thickness profile across a substrate and no deposition near an edge area of the substrate. The area near the edge where deposition is not desired is generally referred to as the “edge exclusion.” FIG. 1A is a partial cross-sectional view showing the desired profile for a deposition layer 102 formed on a substrate 101. The deposition layer 102 is uniformly deposited across a top surface of the substrate 101 and there is no deposition within an edge exclusion area 103. Unfortunately, an actual deposition profile generally differs from the ideal configuration illustrated in FIG. 1A. FIG. 1B is a partial cross-sectional view showing an actual surface profile of a deposition layer 102a on the substrate 101 after having undergone a CVD or PECVD deposition. The deposition layer 102a typically extends to the edge exclusion area 103, and a bevel edge 104 with extra thickness may be formed near the edge exclusion area 103.
To prevent the formation of the deposition film at the edge of the substrate, FIG. 1C is a partial cross-sectional view showing one conventional approach that proposes to use a shadow ring 105. The shadow ring 105 is usually arranged at a location that overlaps and covers at least one portion of the edge exclusion area 103 of the substrate 101. As a result, as shown in FIG. 1C, a deposition layer 102b gradually reduces under the shadow of the shadow ring 105.
While the use of the shadow ring 105 can currently achieve thickness uniformity, or other desired edge profile, within up to a 3.5 mm-wide edge exclusion area, the requirement for thickness non-uniformity, or other desired profile characterestrics, has to be reduced to a 2 mm-wide edge exclusion area owing to increasingly shrinking device dimensions. As a result of the smaller edge exclusion area, the conventional approach using the shadow ring 105 to prevent deposition at the edge area may not provide satisfactory result.
Therefore, there is a need for an apparatus and method for depositing a film on a substrate and removing the film from the substrate edge region in an integrated manner without using a shadow ring.